Surface-finishing agent and finished material and method of surface finishing

ABSTRACT

The present invention provides a surface-treating agent to form fine roughness on the surface of a material and more specifically a surface treating-agent which forms fine roughness on the surface of a material and is easy to process, thereby being useful for materials for highly water-repellent glass, lenses and fabric, materials with an excellent anti-soiling property, panels having an excellent light scattering property, illumination of optical fiber and the like, materials and coatings to prevent accumulation and adhesion of snow or icicle formation on antennas, wires and steel towers, and roughness formation on the surface of semiconductor substrates; the treated materials; and a method of surface treatment to develop the roughness. The surface-treating agent of the present invention has an average primary particle diameter in the range of 1-50 nm, contains fine particles in the range of 5-60% by mass of the total amount of the surface-treating agent in a slurry of nanoparticles which are treated for water repellency and mechanically dispersed in a solvent containing a volatile solvent, and forms a roughness structure with upward protrusions having a spatial periodicity of 0.1-50 μm on the surface of a material by volatilizing the solvent or dipping repeatedly in water upon treating the surface of the material.

FIELD OF THE INVENTION

The present invention relates to a surface-treating agent to form fineroughness on the surface of a material and the material treated withthis surface-treating agent.

Further, the present invention relates to a method of surface treatmentto develop fine roughness on a surface of a material.

More specifically, the invention relates to a surface treating-agentwhich forms fine roughness on a surface of a material and is easy toprocess, thereby being useful for materials for highly water-repellentglass, lenses and fabric; materials with an excellent anti-soilingproperty; panels having an excellent light scattering property;illumination of optical fiber and the like; materials and coatings toprevent accumulation and adhesion of snow or icicle formation onantennas, wires and steel towers; roughness formation on the surface ofsemiconductor substrates; materials for rough surface substrates inwhich a photocatalyst is used together to improve catalytic effect; andfor improving the relative surface area of an exhaust gas treatingcatalyst.

BACKGROUND OF THE ART

Until today, various attempts have been made to form fine roughness on asurface of various materials. For example, a method of forming roughnessby eluting a component from a coating film (Japanese Patent Laid-OpenNo. 2001-17907), a coating film which has fine pores with an averagepore diameter of less than 200 nm and a method of producing the same(Japanese Patent Laid-Open No. 2001-152138), a porous film structurewith a pore diameter of 100 nm to 2 μm and a method of producing thesame (Japanese Patent Laid-Open No. 2001-207123), a method usingexcitation particle beam(http;//www.jvia.gr.jp/j/shinkusangyo/shiryou/thinfilmworld/film23.pdf),and a method using plating, fractal (T. Onda, S. Shinbuichi, N. Satoh,K. Tsujii, Langmuir, 12, 2125-2127 (1996)) have been reported.

DISCLOSURE OF THE INVENTION

In the abovementioned known methods, although a roughness structure canbe formed on a surface of a material, there is a fundamental problem,namely, that the periodic structure is difficult to control, in additionto the disadvantage that the process is complicated and special devicesare necessary for different materials. In particular, the method inJapanese Patent Laid-Open No. 2001-152138 has an industrial disadvantagethat it takes a long time to form the coating film although the coatinghas excellent characteristics such as exhibiting water slipping propertyand forming fine roughness. Further, the method in Japanese PatentLaid-Open No. 2001-207123 has a disadvantage that the resulting coatingfilm has a structure with downward protrusions, which makes the coatingfilm porous and its water-repellency weaker than a coating filmstructure with upward protrusions.

In view of these problems, the present inventors responded with acompletely new unconventional way of thinking. Specifically, the presentinventors utilized a concept of an academic field related to theself-organization in the nonequilibrium system, namely, “DissipativeStructures” to which the Nobel Prize in chemistry was awarded in 1977,and found that a fine roughness structure can be spontaneously formed ona surface of a material simply by coating a material with asurface-treating agent which is designed to form a roughness structureat room temperature under normal pressure. Consequently, the presentinventors found that the roughness structure has high water slippingproperty when it is water-repellent and is utilizable for materials suchas glass, lenses and fabric; materials with an excellent anti-soilingproperty; materials and coatings to prevent accumulation and adhesion ofsnow or icicle formation on antennas, wires and steel towers; roughnessformation on the surface of semiconductor substrates; materials forrough surface substrates in which an photocatalyst is used together toimprove catalytic effect; and for improving the relative surface area ofan exhaust gas treating catalyst. Further, the present inventors foundthat the fine roughness in which the spatial periodicity is controlledhas a function to generate diffused reflection of light uniformly,thereby enabling efficient light-scattering illumination simply byapplying on illumination panels or optical fiber. Further, by using a UVshading material such as titanium oxide and zinc oxide as fineparticles, a UV shading effect can be imparted to glass and the like.

The invention described in the present application comprises the firstto the seventeenth inventions as follows (hereinafter referred to as“the present invention” unless otherwise stated). Namely, the firstinvention is a surface-treating agent characterized in that the averageprimary particle diameter is in the range of 1-50 nm, that it containsfine particles in the range of 5-60% by mass of the total amount of thesurface-treating agent in a slurry of nanoparticles which are treatedfor water repellency and mechanically dispersed in a solvent containinga volatile solvent, and that it forms a roughness structure with upwardprotrusions having a spatial periodicity of 0.1-50 μm on a surface of amaterial by volatilizing the solvent or dipping repeatedly in water upontreating the surface of the material.

The second invention is a surface-treating agent characterized in thatthe average primary particle diameter is in the range of 1-50 nm, thatit contains fine particles in the range of 5-60% by mass of the totalamount of the surface-treating agent in a slurry of nanoparticles whichare treated for water repellency and mechanically dispersed in a solventcontaining a volatile solvent and further a water-repellent resincomponent in the range of 0.1-5% by mass of the total amount of thesurface-treating agent, and that it forms a roughness structure withupward protrusions having a spatial periodicity of 0.1-50 μm on asurface of a material by volatilizing the solvent or dipping repeatedlyin water upon treating the surface of the material.

The third invention is the surface-treating agent further comprisingpolymeric resins including monomers and oligomers in addition to thenanoparticle slurry treated for water repellency.

The fourth invention is the abovementioned surface-treating agentcharacterized in that the treatment for water repellency is selectedfrom alkyl silane treatment, alkyl titanate treatment, and alkylaluminate treatment.

The fifth invention is a material which is obtained by further sinteringa material coated with the abovementioned surface-treating agent and hasa roughness structure with upward protrusions having a spatialperiodicity of 0.1-50 μm on the surface.

The sixth invention is a highly water-repellent material which isobtained by further sintering a material coated with the abovementionedsurface-treating agent and further treating for water repellency and hasa roughness structure with upward protrusions having a spatialperiodicity of 0.1-50 μm on the surface.

The seventh invention is the abovementioned surface-treating agentcharacterized in that the admixing amount of a liquid component having adynamic viscosity of greater than 1×10⁻³ m²/s at the temperature usedfor the surface treatment is less than 10% by mass of the mass of thesurface-treating agent.

The eighth invention is the abovementioned surface-treating agentcharacterized in that the admixing amount of a liquid component having adynamic viscosity of greater than 1×10⁻³ m²/s at the temperature usedfor the surface treatment is less than 3% by mass of the mass ofsurface-treating agent.

The ninth invention is the abovementioned surface-treating agentcharacterized in that the treatment for water repellency is octylsilanetreatment.

The 10th invention is the abovementioned surface-treating agentcharacterized in that the nanoparticles are one or more selected fromtitanium oxide, lower titanium oxide, zinc oxide, zirconium oxide,aluminum oxide, carbon black, silicic acid anhydride, cerium oxide,gold, silver, platinum, palladium, rodium, lanthanum, vanadium,tungsten, iron oxide, iron hydroxide and cobalt oxide.

The 11th invention is a surface-treating agent characterized in that itforms a roughness surface exhibiting an efficient photocatalytic effectby admixing a photocatalyst at a concentration not to interfere withroughness formation, namely in less than 5% of the mass of thesurface-treating agent.

The 12th invention is the abovementioned surface-treating agentcharacterized in that a wet medium type pulverizer is used as a methodof mechanically dispersing nanoparticles treated for water repellency.

The 13th invention is the abovementioned surface-treating agentcharacterized in that it further comprises one or more volatile solventshaving a boiling point in the range of 40-99° C. at one atm.

The 14th invention is the abovementioned surface-treating agentcharacterized in that the boiling point of a volatile solvent used uponpreparing a slurry of nanoparticles treated for water repellency is inthe range of 100-260° C. at one atm.

The 15th invention is the abovementioned surface-treating agentcharacterized in that the volatile solvent used upon preparing a slurryof nanoparticles treated for water repellency is one or more selectedfrom decamethylcyclopentasiloxane, methyl trimethicone, andtetrakistrimethylsiloxy silane.

The 16th invention is the abovementioned material characterized in thatit is a raw material selected from glass, silicon wafer, fiber,synthetic resins, optical fiber, and gas exhaust treating catalysts, ora structure comprising said raw material.

The 17th invention is a method of surface treatment characterized inthat a material coated with the abovementioned surface-treating agent isdried and then father soaked in water, thereby further developingroughness on the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a scanning electron microscopic photograph ofExample 1.

FIG. 2 shows the result of measurements for optical characteristics whena glass plate was treated with the surface-treating agent of Example 1,using a multi-angle spectrophotometer by Murakami Color ResearchLaboratory Co. Ltd. (Goniophotometer, type GSP-2; incident angle: 45degrees; receiving angle: −80 to 80 degrees).

FIG. 3 shows the result of measurements for optical characteristics whena glass plate was treated with the surface-treating agent of ComparativeExample 1, using the multi-angle spectrophotometer in the same manner asin Example 1.

FIG. 4 shows the result of measurements for optical characteristics whena glass plate was treated with the surface-treating agent of ComparativeExample 2, using the multi-angle spectrophotometer in the same manner asin Example 1.

FIG. 5 shows an example of a scanning electron microscopic photograph ofExample 4.

FIG. 6 shows an example of a scanning electron microscopic photographwhen an aluminum plate was coated with the surface-treating agent ofExample 5 and sintered at 300° C.

FIG. 7 shows an example of scanning electron microscopic photograph whena glass plate was coated with the surface-treating agent of Example 5and sintered at 300° C.

FIG. 8 shows an example of scanning electron microscopic images when aglass plate was coated with the surface-treating agent of Example 5 andsintered at 500° C.

BEST MODE TO CARRY OUT THE INVENTION

The present invention will be explained in detail as follows.

First, the principle of the roughness structure formation of the presentinvention is explained.

The surface-treating agent of the present invention has an averageprimary particle diameter in the range of 1-50 nm, and contains fineparticles in the range of 5-60% by mass of the total amount of thesurface-treating agent in a slurry of nanoparticles which are treatedfor water repellency and mechanically dispersed in a solvent containinga volatile solvent, and occasionally it contains a water-repellant resincomponent in the range of 0.1-5% by mass of the total amount of thesurface-treating agent.

In order to simplify the explanation of the invention, a system ischosen as an example, in which 20% ethanol is admixed to a slurry ofnanoparticles treated for water repellency containing fine particlesdispersed in a volatile cyclic silicone in an amount of about 20% bymass.

The formulation thus prepared has an appearance of a liquid slurry. Whenthis slurry is thinly coated, for example, on a glass plate, ethanolquickly starts to volatilize at room temperature of about 30° C. Ethanolvolatilizes faster from the surface of the coating film than from theinside of the coating film and thus the concentrations of the fineparticles and the cyclic silicone on the surface of the coating filmbecome higher than those in the inside of the coating film.

However, fluidity is sustained because the cyclic silicone remains. Inthis state, shrinkage force acts on the surface of the coating film andthe shrinkage force is generated unevenly due to fluctuation inconcentration under this circumstance. However, diffusion of substanceswhich set off such fluctuation in concentration also takes place at thesame time.

Here, according to the theory of Dissipative Structures (see Kondepudi,D. K. and Prigogine, I. (1988), Modern Thermodynamics—From Heat Enginesto Dissipative Structures, John Wiley & Sons, New York, Chap. 19:Dissipative Structures, pp. 427-457), the time required to suppress thefluctuation due to diffusion competes with the time required forshrinkage and thus a structure of spatial fluctuation of criticalwavelength develops, thereby forming a structure having a spatialperiodicity with certain intervals.

For example, in the abovementioned state, a roughness structure having aspatial periodicity of one to several μm can be formed usingmechanically dispersed fine particles of octyl silylated titanium oxideas nanoparticles treated for water repellency. On the contrary, whenlarge fine particles such as pigment grade titanium oxide particles witha size of 200 nm are used alone, shrinkage force cannot affectefficiently because the size of the fine particles is too large so thatthere is no competition of force to form the structure. Further, when awater-repellent resin component is admixed in a large amount, thematerial diffusion is weakened and loses its competition of force,thereby no fluctuation being developed to form the structure; however,when the resin component is used in the range given in the presentinvention, fluidity of the coating film remains thus the structure canbe formed. When the abovementioned nonvolatile component consists offine particles alone, the resulting structure is physically complete butthe coating film is disadvantageously decomposed by a surfactant or thelike; however, when the water-repellent resin component is admixed, theresulting coating film is a firm structure comprising the fine particlesand resin and characterized by its excellent durability. Accordingly,electron microscopic observation of the top of the roughness partobtained in the present invention shows the fine particles not singlybut as linear structures.

The coating film formation by utilizing such a force competition offorce of the theory of Dissipative Structures has not conventionallyexisted; the structure cannot be formed even if similar components arecontained unless the force balance is intentionally changed.

Accordingly, in the present invention, it is necessary to be able toform a roughness structure with upward protrusions having a spatialperiodicity of 0.1-50 μm by admixing a specific component in a certainratio as mentioned above and further volatilizing a solvent orrepeatedly dipping in water. The surface structure with upwardprotrusions means the state that the roughness with upward protrusionsis formed after the roughness formation whereas the interface is smoothimmediately after coating with a surface-treating agent; the expression“with downward protrusions” means the state that there are open holes onthe smooth interface immediately after coating with a surface-treatingagent. It is obvious from electron microscopic observation that thecoating film treated with the surface-treating agent has upwardprotrusions. Generally, ordinary surface-treating agents contain ahighly viscous oily agent as an ingredient, or have extremely high orlow volatility and thus are designed to provide a smooth surface coatingfilm; these known technologies are different from those of the presentinvention.

The nanoparticles treated for water repellency to be used in the presentinvention have an average primary particle diameter in the range of 1-50nm; this average primary particle diameter is obtained by observation ofparticle size distribution using an electron microscope.

Further, when secondary agglomerates present in the surface-treatingagent have an average particle diameter of greater than 200 nm and thenumber of the secondary particles exceeds 30% of that of the entireparticles, no coating film having substantial periodicity is formed evenwhen the primary particle diameter is within the abovementioned range,which is considered to be beyond the scope of the present invention.

In the present invention, one or more kinds of nanoparticles treated forwater repellency exhibiting this range of particle distribution arecombined. An example of the treatment for water repellency to be used inthe present invention is preferably a treatment not to disperse in a 10%by mass ethanol aqueous solution, such as alkyl silane treatment, alkyltitanate treatment, alkyl aluminate treatment, silicone (methylhydrogenpolysiloxane) treatment, pendant treatment (addition of an olefincompound after methylhydrogen polysiloxane treatment), metal soaptreatment, end-reactive silicone treatment, end-reactiveperfluoropolyether treatment, fluoroalkylsilane treatment, treatmentwith perfluoroalkyl phosphate and salts thereof, and treatment with asilane coupling agent.

In the present invention, they may be used alone or in combination ofmore thanone. Among them, alkyl silane treatment, alkyl titanatetreatment, and alkyl aluminate treatment, which can particularly improvedispersion of the fine particles, are preferable and octylsilylationtreatment is particularly preferable. Further, as to fine particlestreated with a fluorine compound, when the amount to be mixed isincreased, phase separation occurs in the process of drying apreparation, which makes it difficult to control the coating, and thefine particles treated with a fluorine compound are often waterrepellent and oil repellent and thus poorly immobilized onto a surfaceof a treated material, which may result in elimination and agglomerationof the fine particles in contact with water or snow; accordingly, whenadmixed to a preparation, the amount is preferably controlled in therange of 0.001-30% by mass of the total amount of the nanoparticlestreated for water repellency. Further, as also shown in a comparativeexample of the present invention, fine particles treated with a fluorinecompound show a high contact angle when a water droplet is droppedgently on the coating film, whereas in moving water, the entire coatingfilm gets wet and water repellency is occasionally lost.

The fine particles used in the present invention are one or moreselected preferably from titanium oxide, lower titanium oxide, zincoxide, zirconium oxide, aluminum oxide, carbon black, silicic acidanhydride, cerium oxide, gold, silver, platinum, palladium, rodium,lanthanum, vanadium, tungsten, iron, iron oxide, iron hydroxide, cobaltoxide, cobalt hydroxide, zinc phosphate, barium sulfate, magnesiumaluminosilicate, calcium aluminosilicate, hydroxyapatite, tin oxide,silicon carbonate, silicon nitride, titanium nitride, indium oxide/tinoxide complex, and complex compounds thereof; in particular, thenanoparticles are one or more preferably selected from titanium oxide,lower titanium oxide, zinc oxide, zirconium oxide, aluminum oxide,carbon black, silicic acid anhydride, cerium oxide, gold, silver,platinum, iron oxide, iron hydroxide, and cobalt oxide. Further, thekind of fine particles is preferably changed depending on the purpose ofsurface treatment. For example, when the treatment is for protectionfrom ultraviolet rays, titanium oxide, zinc oxide, and cerium oxide arepreferably used; when the treatment is for light scattering, titaniumoxide having a high refractive index is preferably admixed; for thepurpose of securing transparency, silicic acid anhydride is preferablyused.

The shape of the fine particles used in the present invention can bevarious including rod, spindle, round, and amorphous shapes. Further, itis also preferable to perform surface pretreatment with a compound suchas silica, alumina and zinc phosphate for the purpose of suppressingcatalytic activity of the fine particles.

Examples of the method of treating for water repellency used in thepresent invention include a wet mixing method using a solvent, a gasphase method such as CVD, and a dry mixing method; however, the wetmixing method is most preferable because it secures the uniformity ofthe treatment. In particular, it is preferable to perform surfacetreatment while carrying out pulverization using a wet medium type millsuch as a bead mill and a sand mill. Further, it is preferable to addheat treatment for the purpose of completing the treatment.

A slurry used in the present invention contains nanoparticles treatedfor water repellency which have an average primary particle diameter inthe range of 1-50 nm and are mechanically dispersed in a solventcontaining a volatile solvent. Examples of the method of mechanicallydispersing the nanoparticles treated for water repellency include amethod of pulverization using a wet medium type pulverizer, a methodusing a roll mill and a method in which a slurry is ejected under highpressure; however, the method using a wet medium type pulverizer, whichis easy to manage and excellent for mass production, is most preferred.

Examples of the volatile solvent used in the present invention includepreferably one or more selected from decamethylcyclopentasiloxane,methyl trimethicone, tetrakistrimethyl siloxy silane, volatile linearsilicones, alkyl modified silicones, fluorocarbon, toluene, hexane,cyclohexane, petroleum ether and light isoparaffin. In particular, it ispreferred to use a volatile solvent having a boiling point in the rangeof 100-260° C. at one atm, which is highly safe for work. This range isadvantageous to provide highly safe working conditions for mechanicalpulverization. Such examples include decamethylcyclopentasiloxane(boiling point: 210° C.), methyl trimethicone (boiling point: 190° C.)and tetrakistrimethyl siloxy silane (boiling point: 222° C.).

In the present invention, a nonvolatile solvent can be used togetherwith these volatile solvents; however, the final content of anonvolatile oily solvent has to be not more than 20% by mass of thesurface-treating agent. When the amount of the nonvolatile oily agentexceeds 20% by mass, shrinkage force on the coating surface becomes weakand the structure formation is difficult and moreover the strength ofthe resulting structure is disadvantageously decreased. Further, thecontent of the nanoparticles treated for water repellency in the slurryused in the present invention is preferably in the range of 5-55% bymass, more preferably 25-50% by mass, of the total amount of the slurry.When it is less than 5% by mass, the amount of the fine particles is toosmall to control the coating film structure, while when it exceeds 55%by mass, secondary agglomerates of the fine particles cannotsufficiently be disintegrated into primary particles and a large amountof agglomerated particles are mixed, which makes it disadvantageouslydifficult to form a roughness structure of the coating film. The fineparticles in a slurry of nanoparticles treated for water repellency usedin the present invention are preferably dispersed as uniformly aspossible. When they are uniformly dispersed, a uniform roughnessstructure can be formed.

Further, in the present invention, it is possible to admix nanoparticleswithout treatment for water repellency and pigments together withnanoparticles treated for water repellency; however, the content ofadmixing has to be minimized because they interfere with the structureformation. More specifically, the content is preferably not more than20% by mass of the nanoparticles treated for water repellency.

In the present invention, the average primary particle diameter is inthe range of 1-50 nm and the fine particle content is in the range of1-60% by mass of the total amount of the surface-treating agent, in aslurry of nanoparticles which are treated for water repellency andmechanically dispersed in a solvent containing a volatile solvent. Aroughness structure can be stably formed in this range. When the contentis less than 1% by mass, the structure cannot be formed; when thecontent exceeds 60% by mass, the concentration of the fine particles istoo high and agglomeration of the fine particles or the like occurs,which occasionally results in an uneven roughness structure of thecoating film.

In the present invention, one or more volatile solvents having a boilingpoint in the range of 40-99° C. at one atm are preferably contained atthe same time. Examples of the volatile solvents having a boiling pointof this range include lower alcohols such as ethyl alcohol (boilingpoint: 78° C.), propyl alcohol (boiling point: 97° C.) and isopropylalcohol (boiling point: 83° C.); ethyl alcohol and isopropyl alcohol areparticularly preferable.

In the present invention, the content of this volatile solvent is in therange of 2-60% by mass of the total amount of the surface-treatingagent. In this range, advantageously, the shrinkage force of the coatingfilm effectively functions.

Further, when the content is less than 2% by mass, there arises aproblem that the shrinkage force of the coating film is weak so that thestructure is difficult to form; when the content exceeds 60% by mass,volatility becomes high so that there arises problems that uniformcoating film with the surface-treating agent is difficult to form andthat the solvent concentration in the working environment increases,although the solvent is effective for sterilization of the coating film.

These conditions are based on the consideration that the work is carriedout in an open system at atmospheric pressure; when specific solventrecovering apparatus or coating apparatus is used, it is possible to usea more highly concentrated or non-mixed solution.

The surface-treating agent of the present invention is characterized inthat when used for treating a surface of a material, it forms aroughness structure with upward protrusions having a spatial periodicityof 0.1-50 μm on the surface by volatilizing a solvent or repeatedlydipping in water. Examples of the method for surface treatment aresimple and include a method of immersing a material in thesurface-treating agent, a method of coating with the surface-treatingagent using a brush, a method of coating with the surface-treating agentusing a spray and a method by printing; however, the method by printingis preferable.

The thickness of the coating film upon coating with the surface-treatingagent of the present invention is in the range of 0.5-100 μm; the rangeof 1-10 μm is more preferable to be able to obtain an orderly roughnessstructure. In this range, the roughness structure of the coating filmcan advantageously be formed more firmly.

Further, the reaction is carried out at a temperature in the range ofpreferably 20-60° C., more preferably 35-45° C. In this range, thevolatilizing speed of the volatile solvent is appropriate to form theroughness structure.

In the present invention, it is possible to further develop theroughness structure by repeatedly dipping a material in water at thestage where the coating film gets dry after treating the material withthe surface-treating agent. This is because shrinkage force greater thanthe surface shrinkage force generated upon volatilizing the volatilesolvent is obtained due to hydrophobicity of the fine particles, thesolvent and the resins. The roughness structure is preferably confirmedby a noncontact type surface micro roughness meter or an electronmicroscope.

Further, the spatial periodicity can be confirmed, for example, by amethod in which a photograph obtained using an electron microscope isprocessed into data using an image scanner and the spatial periodicityis confirmed from a power spectrum by using an image analysis software(for example, a spatial periodicity analysis software distributed by USANational Institute of Health (NIH) http://www.nih.gov/). The roughnessof the coating film obtained by the theory of Dissipative Structuresused in the present invention has a spatial periodicity of 0.1-50 μm.When the spatial periodicity is less than 0.1 μm, characteristics suchas water repellency is not desirable while when the spatial periodicityexceeds 50 μm, the roughness of the coating film is not perfectlycontrolled and thus the coating film cannot uniformly formed.

In the present invention, it is preferable that the periodic structureof the coating film is uniformly formed in the entire coating film;however, when more than 50% of the coated area show the roughnessstructure, it is considered to satisfy the present invention sinceununiformity is occasionally generated due to various conditions (forexample, coating conditions, the amount of coating). In the case of lessthan 50%, various characteristics (water repellency, optical properties,snow resistance, and the like) attributed to the roughness structurebecome disadvantageously deteriorated. The amount of coating of thesurface-treating agent of the present invention depends on thecharacteristics of a material; however, the amount of approximately0.01-2 mg/cm² is preferably coated on the surface of the material. Whenthe amount is less than 0.01 mg/cm², a uniform coating film is difficultto be formed. When the amount exceeds 2 mg/cm², the roughness formationmay be insufficient in some areas.

It is best confirmed by electron microscopic observation whether thesurface-treating agent of the present invention is a preparation whichcan form the roughness structure based on the theory of DissipativeStructures; however, a periodic structure may be considered to be formedwhen the contact angle measured after treatment with water is more than10 degrees higher than that measured before treatment with water, inwhich, for example, a glass plate treated with the surface-treatingagent on the surface in an amount of coating of 0.25 g/cm² is dried at37° C. for 10 minutes under air flow and repeatedly placed in and out ofrunning water (4 L/min) at 35° C. for one minute at a rate of 100times/min slanting at an angle of 30 degrees from the horizontal.Contrarily, the contact angle remains the same or decreases aftertreatment with water when the periodic structure is not formed. However,since this measuring method is a simplified one, there are cases wherethe measurement shows no increase in the contact angle while thestructure is observed by electron microscopic observation, although veryrarely.

Examples of the water-repellent resin component used in the presentinvention include one having a property to be dissolved in a volatilesolvent, further a water-repellent resin component such as siliconeresins, and one produced by chemically modifying a hydrophilic resincomponent into water-repellent one such as siliconated pullulane. Thewater-repellent resin component can be any resin component ordinarilyused, including trimethylsiloxy silicate, peroxyfluoroalkylated siliconeresins, acrylic silicone, polyamide modified silicones, alkyl modifiedsilicones, polystyrene, nitrocellulose, ethylcellulose, alkyl acrylates,alkyl methacrylates, modified alkyd resins, and carnauba wax. Theadmixing amount of the water-repellent resin component used in thepresent invention is, for example, in the range of 0.1-5% by mass of thetotal amount of the surface-treating agent. In this range, the fineparticles can be immobilized onto a material, forming the roughnessstructure. Disadvantageously, the immobilization of the fine particlesbecomes weak when the amount is less than 0.1% by mass and the roughnessstructure is difficult to be formed when the amount exceeds 5% by mass.

In the present invention, the coating film obtained as abovementionedcan be immobilized onto a material by sintering altogether with thematerial. Since the roughness structure according to the presentinvention is merely a structure comprising fine particles, a resincomponent, and additives to be mentioned later, it is not durable forlong-time use, such as use for auto glass. Here, by sintering thecoating film itself, the roughness structure of the coating film can befirmly immobilized onto the surface of the material. In this case, thetemperature for sintering is preferably, for example, in the range of300-800° C. Disadvantageously, carbon remains and coloring occurs whenthe temperature is too low and the material itself may melt so that thestructure of the coating film cannot be maintained when the temperatureis too high. However, when treatment is sintering alone, the roughnessstructure is hydrophilic or poorly water-repellent and lackscharacteristics such as water slipping property; accordingly, dependingon the usage, the surface of the coating film is further treated forwater repellency, for example, by silicone treatment, fluorine compoundtreatment, or silane treatment to obtain excellent characteristics.

In sintering, together with the surface-treating agent, a nonvolatilesilicone oil, one having a dynamic viscosity preferably in the range of1-30×10⁻⁶ m²/s, is preferably used. In this case, the silicone oil ischemically changed into silica upon sintering to immobilize the fineparticles, thereby advantageously improving the strength of the coatingfilm.

Examples of the material used in the present invention include rawmaterials, such as glass, silicon wafer, fiber, synthetic resins,building materials, optical fiber, resin film, the surface of steeltowers or the bottom of ships to be coated, wire, metal plates,semiconductor substrates, ceramics and exhaust gas treating catalysts(e.g., denitrification apparatus, ternary catalysts), and structurescomprising said materials; in particular, raw materials such as glass,silicon wafer, fiber, synthetic resins, optical fiber, exhaust gastreating catalysts or structures comprising said materials arepreferable.

In the present invention, it is possible to admix various kinds of oilagents, pigments, color materials (coloring agents), additives, UVabsorbing agents, antioxidants, surfactants, preservatives and the likein addition to the abovementioned ingredients; however, the admixingamount of a liquid component having a dynamic viscosity of greater than1×10⁻³ m²/s at the temperature used for the surface-treating agent ispreferably less than 10% by mass, more preferably less than 3% by mass,of the amount of the surface-treating agent. This is because the oilysolvent having a dynamic viscosity of greater than 1×10⁻³ m²/sinterferes with shrinkage force and diffusion associated withvolatilization of the volatile solvent and affects in the direction tosuppress the development of fluctuation, which makes the periodicstructure formation difficult. Here, the standard of this dynamicviscosity is a dynamic viscosity at the time of use of thesurface-treating agent; accordingly for components such as reactivemonomers whose viscosity is low upon processing but increases with time,a dynamic viscosity at the original monomer state is to be applied.Further, when the dynamic viscosity cannot practically be measured dueto factors such as a high surface treatment temperature andvolatilization, the measurement can be carried out under controllableconditions such as at room temperature.

In the present invention, the total amount of these additive components,excluding water-soluble components such as water and polyvalentalcohols, is preferably less than 30% by mass, more preferably less than20% by mass, of the total amount of the surface-treating agent. In thisform of preparation, the water-soluble components are known to havelittle effect on the structure formation of the coating film but othercomponents, particularly oil-soluble components, often affect thestructure formation and the spatial periodicity. Further, pigments/colormaterials (in this case, those having a primary particle diameter of 50nm to 1 mm) can be admixed; however it is preferable that the totaladmixing amount is limited to in the range of 0.0001-20% by mass of thetotal amount of the surface-treating agent and that the surface istreated for water repellency in the same manner as for theabovementioned nanoparticles. Further, the abovementioned nanoparticlesare preferably admixed in an amount equal to or greater than the mass ofthe pigments/color materials.

These pigments/color materials do not form the structure because of theabovementioned reasons but can form the structure in combination withthe abovementioned nanoparticles. However, in case the abovementionednanoparticles are combined, the amount of admixing is preferably limitedwithin the abovementioned range because when the amount of thepigments/color materials is too much, substance diffusion is interferedwith and thus the structure cannot be formed. Further, among thepigments, in particular, particles exhibiting photocatalytic activity,i.e., anatase-type titanium oxide, precious metal-containing titaniumoxide, and pigment-containing titanium oxide, with an average primaryparticle diameter in the range of 5 nm to 0.3 um can be used to obtain afunction as an anti-soiling material.

In admixing, the amount of these photocatalysts is preferably less than10%, more preferably less than 5%, of the mass of the surface-treatingagent of the present invention. However, since the roughness formationis occasionally interfered with depending on the dispersive state of thephotocatalytic particles, it is important to admix the photocatalysts ina concentration not to interfere with the roughness formation, forexample, simultaneously using mechanical dispersion, to form a roughnesssurface having photocatalytic effects. A photocatalyst-contacting areacan be advantageously increased by the roughness formation.

In the present invention, monomer reactive raw materials are alsopreferably used together with the abovementioned components. Examples ofmonomer reactive raw materials include various known compounds includingheat reactive compounds, photoreactive compounds (ultravioletlight-reactive compounds, ultra red light-reactive compounds), electronbeam- or plasma-reactive compounds, compounds which react with catalyst,radical reactive compounds, and compounds which form cross-linkedcompounds by reacting with metal ions, such as unsaturated fatty acids.

Examples of polymeric resin compounds including these monomers andoligomers include those containing one or more compounds selected, forexample, from epoxy compounds, acrylamide monomers (e.g., acrylamide,N-isopropylacrylamide), acrylic monomers (e.g., acrylic acid,methacrylic acid, isobutyl acrylate), acrylic oligomers, drying oil(e.g., linseed oil, poppy oil), polyvinyl cinnamate compounds,unsaturated polyester compounds, dichromic acid compounds, ene-thiolcompounds, modified silicone compounds, silane compounds such asvinylsilane and silane coupling agents, allyl diglycol carbonates,multifunctional cyclic carbonate compounds, multifunctional (metha)acrylates (e.g., urethane (metha) acrylate, epoxy (metha) acrylate),cyanoacrylate, phthalic acid compounds and acrylsilicone compounds;however, since compounds having a boiling point of lower than 100° C. atone atm volatilize by themselves and are difficult to control, theirboiling points at one atm are preferably changed to higher than 100° C.by oligomerization or the like.

Further, as to reaction assisting components or reaction initiatingagents such as photoreaction initiating agents and radical reactioninitiating agents or ion supplementing agents, the abovementionedlimitations are not applied. However, when these monomer reactive rawmaterials are used in environments such as outdoors, at room temperatureor at an atmospheric temperature, the admixing amount of the liquidcomponent having a dynamic viscosity at 25° C. of more than 1×10⁻³ m²/sis preferably less than 10% by mass, more preferably less than 3% bymass, of the mass of the surface-treating agent. However, when thetreatment is carried out at a higher temperature or under reducedpressure in a closed atmosphere, the amount of admixing is not limitedas long as the dynamic viscosity at the temperature used is less than1×10⁻³ m²/s.

The formulation of the present invention can be an emulsion type, asolvent type, or a multilayer separation type; however, the multilayerseparation type which is shaken or stirred upon use is preferable.

An example of a method of designing the surface-treating agent of thepresent invention is shown as follows.

First, the kind of nanoparticles is determined to meet the purpose ofuse. For example, when UV light is involved, a material such as titaniumoxide, zinc oxide, tungsten oxide, and cerium oxide can be used; whenlight scattering is involved, zinc oxide, silica dioxide, zirconiumoxide, and the like are preferable; when catalysis is involved, ceriumoxide, platinum, rodium, palladium, and the like are preferable; whenwater repellency is of interest, titanium oxide, cerium oxide, silicadioxide, zirconium oxide, and the like are preferable; and as ananti-soiling material, titanium oxide having a photocatalytic activityis preferable. Next, these nanoparticles are treated for waterrepellency, in which it is necessary to disintegrate agglomerates and toprevent reagglomeration since the nanoparticles are stronglyagglomeratable.

An example of an excellent surface treatment which is effective inpreventing reagglomeration is a treatment with octyltriethoxy silane, inwhich the nanoparticles and octyltriethoxy silane are simultaneouslywet-pulverized in a solvent and thus cut faces successively react withoctyltriethoxy silane, thereby reagglomeration is prevented to obtain ahighly dispersive treating powder. This material can be used as it is ormade into a slurry by returning it into the solvent. Preparations areprepared by admixing this slurry in concentrations by 10% difference,components to immobilize the coating film such as adhesives, resins, andreactive compounds in various levels of concentrations and a volatilesolvent to total 100%. Next, differences in the contact angle after andbefore treatment with water for the individual sample preparations areobtained to draw a graph, thereby the ranges in which the contact angleincreases specifically to these ingredients being obtained. This rangegenerally agrees with the range where the roughness periodic structureis formed based on the theory of Dissipative Structures. After thisrange is set, other substantially necessary components such as additivesand coloring agents are added to these ingredients of this range atvarious admixing levels and the similar procedure is carried out. Inthis way, a composition exhibiting a large contact angle difference andin the range agreed with the purpose of use is searched and thus acomposition of the surface-treating agent of interest can be obtained.

The following examples and comparative examples will explain the presentinvention more in detail.

Further, methods for evaluation of various characteristics used in theexamples and comparative examples are shown as follows.

(1) Method of Measuring Contact Angle

One side of a glass plate (5 cm×10 cm×3 mm) having a hydrophilic surfacewas coated with 12 mg of a surface-treating agent and dried at 37° C.for 10 minutes using an air blow dryer. The contact angle was measuredfrom photographic data immediately after contact with a water dropletusing a contact angle measurement apparatus (contact angle measurementapparatus (Type CA-DT) by Kyowa Interface Science). Further, the contactangle was measured after placing this glass plate in and out of runningwater (4 L/min) for one minute at a rate of 100 times/min slanting at anangle of 30 degrees from the horizontal.

(2) Confirmation of Roughness and Measurement of Spatial Periodicity

By using a scanning electron microscope, the roughness formation wasconfirmed from a photograph measured at a magnitude of 3000 and thespatial periodicity was measured from a power spectrum of the photographusing the abovementioned NIH image software.

EXAMPLE 1

40 parts by mass of octylsilylated fine particle titanium oxide(silica/alumina-treated fine particle titanium oxide treated with 10% bymass octyltriethoxy silane; average particle diameter: 35 nm; beingdried and heated after reacting in a bead mill using toluene as asolvent) and 60 parts by mass of decamethylcyclopentasiloxane (a kind ofcyclic volatile silicones; boiling point: 210° C.) were roughly mixedand then finely pulverized using a bead mill (a horizontal sand grindingmill) to obtain a slurry of octylsilylated fine particle titanium oxidein which octysilylated titanium oxide fine particles were uniformlydispersed.

Further, 45 parts by mass of octylsilylated fine particle zinc oxide(fine particle zinc oxide treated with 10% by mass octyltriethoxysilane; average particle diameter: 10 nm; being dried and heated afterreacting in a bead mill using toluene as a solvent) and 55 Parts by massof decamethylcyclopentasiloxane were roughly mixed and then finelypulverized using a bead mill (a horizontal sand grinding mill) to obtaina slurry of octylsilylated fine particle zinc oxide in whichoctylsilylated zinc oxide fine particles were uniformly dispersed.

Using these materials, a product (a surface-treating agent whichexhibits light scattering) was obtained with the ingredients shown inTable 1.

Here the unit in Table 1 is % by mass. TABLE 1 Component AOctylsilylated fine particle titanium oxide slurry 1 Octylsilylated fineparticle zinc oxide slurry 40 Methyl trimethicone 10 Dimethylpolysiloxane (KF96A10cs, Shin-Etsu Chemical 10 Co., Ltd.)Trifluoropropylated trimethylsiloxysilicate 50% by mass 2decamethylcyclopentasiloxane solution Decamethylcyclopentasiloxane 8Sorbitan monoisostearate 1 Component B Ethyl alcohol 5 PreservativeAppropriate Anti-mold agent Appropriate Component C Purified waterBalance

After homogeneously mixing component A, component B in solution wasadded and then component C was added, after which the resultingadmixture was stirred and then filled into a container to make theproduct.

The product of Example 1 had a contact angle of 80 degrees and a contactangle after treatment with water of 105 degrees, which showed waterrepellency.

An example of the electron microscopic photograph of the product ofExample 1 is shown in FIG. 1.

The result of the analysis of this photograph showed that the spatialperiodicity was about 1 μm.

The scanning electron microscopic photograph of FIG. 1 shows a size of10 μm in length and 13.3 μm in width.

Further, optical characteristics were measured when a glass plate wastreated with the surface-treating agent of Example 1, using amulti-angle spectrophotometer (Goniophotometer by Murakami ColorResearch Laboratory Co., Ltd., Type GSP-2; incident angle: 45 degrees;receiving angle: −80 to 80 degrees). The result is shown in FIG. 2.

Here the sample was coated in an amount of 1 mg/cm² and dried at 37° C.for 15 minutes.

The result in FIG. 1 reveals that the product of Example 1 exhibits aperiodic structure. It is also revealed that the product of Example 1scattered light uniformly and highly efficiently as shown in data inFIG. 2, although it appears transparent.

EXAMPLE 2

A glass plate was coated with the surface-treating agent of Example 1 inan amount of 0.25 mg/cm² and dried at 37° C. for 60 minutes, after whichit was heated at 500° C. for one hour in a sintering oven.

The resulting coating film was hydrophilic but it maintained the coatingfilm roughness structure similar to that mentioned above.

EXAMPLE 3

The surface-treated glass plate of Example 2 was coated with a 5% bymass isopropyl alcohol solution of perfluoroalkyl phosphate ester anddried at 80° C. for 3 hours.

The coating film thus obtained showed extremely high water repellency.

COMPARATIVE EXAMPLE 1

50 parts by mass of octylsilylated pigment-grade titanium oxide(pigment-grade titanium oxide treated with 10% by mass octyltriethoxysilane; average particle diameter: 250 nm; being dried and heated afterreacting in a bead mill using toluene as a solvent) and 50 parts by massof decamethylcyclopentasiloxane were roughly mixed and then finelypulverized using a bead mill (a horizontal sand grinding mill) to obtaina slurry of octylsilylated pigment-grade titanium oxide in whichoctylsilylated pigment-grade titanium oxide particles was uniformlydispersed. 32 parts by mass of the slurry of octylsilylatedpigment-grade titanium oxide, 20 parts by mass of ethanol, and 48 partsby mass of decamethylcyclopentasiloxane were mixed and filled into acontainer to obtain a product.

The product of Comparative Example 1 exhibited a contact angle of 140degrees and a contact angle after treatment with water of 141 degrees,which showed water repellency.

The result of scanning electron microscopic observation of the productof Comparative Example 1 revealed that the fine particles of the productof Comparative Example 1 were agglomerated and showed no periodicstructure.

Further, optical characteristics were measured when a glass plate wastreated with the surface-treating agent of Comparative Example 1, in thesame manner as described in Example 1 using a multi-angle opticalphotometer. The result is shown in FIG. 3.

Here the sample was coated in an amount of 1 mg/cm² and dried at 37° C.for 15 minutes. FIG. 3 reveals that with the product of ComparativeExample 1, reflectivity in the direction of regular reflection was highand thus uniform scattering was not exhibited.

COMPARATIVE EXAMPLE 2

Using the slurry of octylsilylated fine particle titanium oxide and theslurry of octylsilylated fine particle zinc oxide of Example 1, asurface-treating agent was prepared with the ingredients shown in Table2. TABLE 2 Octylsilylated fine particle titanium oxide slurry 2Octylsilylated fine particle zinc oxide slurry 46 Methyl trimethicone 20Dimethyl polysiloxane (KF96A10cs, Shin-Etsu Chemical Co., Ltd.) 10Methyl alcohol 20

The product of Comparative Example 2 exhibited a contact angle of 108degrees and a contact angle after treatment with water of 108 degrees,which showed water repellency.

The result of scanning electron microscopic observation of the productof Comparative Example 2 revealed that the product of ComparativeExample 2 exhibited no periodic structure.

Further, optical properties were measured when a glass plate was treatedwith the surface-treating agent of Comparative Example 2 in the samemanner as described in Example 1 using a multi-angle spectrophotometer.The result is shown in FIG. 4.

Here the sample was coated in an amount of 1 mg/cm² and dried at 37° C.for 15 minutes.

FIG. 4 reveals that with the product of Comparative Example 2,reflectivity in the direction of regular reflection was high and thusuniform scattering was not exhibited.

COMPARATIVE EXAMPLE 3

16 parts by mass of silica/alumina-treated fine particle titanium oxidetreated with 5% by mass perfluoroalkyl phosphate ester diethanolaminesalt (average particle diameter: 35 nm), 64 parts by mass ofdecamethylcyclopentasiloxane, and 20 parts by mass of ethyl alcohol wereadmixed and pulverized and the resulting solution is filled into acontainer to make a product (surface-treating agent).

The product of Comparative Example 3 exhibited such a high contact angleas 145 degrees after coating and 140 degrees after treatment with water;however, in running water, the entire coating film immediately becamewet and no substantial water repellency was exhibited.

Accordingly, data after treatment with water were obtained by measuringa sample which was dried at 37° C. for 10 minutes after treatment withwater. Further, no orderly periodic structure was formed.

COMPARATIVE EXAMPLE 4

16 parts by mass of silica/alumina-treated fine particle titanium oxidetreated with 5% by mass perfluoroalkyl phosphate ester diethanolaminesalt (average particle diameter: 35 nm), 60 parts by mass ofdecamethylcyclopentasiloxane, 20 parts by mass of ethyl alcohol, and 4parts by mass of a trifluoropropylated trimethylsiloxy silicate solution(a 50% by mass decamethylcyclopentasiloxane solution) were admixed andpulverized and the resulting solution was filled into a container tomake a product (surface-treating agent). The product of ComparativeExample 4 exhibited such a high contact angle as 149 degrees aftercoating and 141 degrees after treatment with water; however, in runningwater, the entire coating film immediately became wet and no substantialwater repellency was exhibited. Accordingly, data after treatment withwater were obtained by measuring a sample which was dried at 37° C. for10 minutes after treatment with water, in the same way as in ComparativeExample 3. Further, no orderly periodic structure was formed.

From the results above, it is revealed that simple coating of theproducts of Examples of the present invention forms a fine roughnessstructure with upward protrusions and provides excellent waterrepellency and optical characteristics. Contrarily, in ComparativeExamples, the fine roughness structure was either not or ununiformlyformed and the optical characteristics were also inferior.

The followings are an example in which drying oil (room temperaturesetting resin) was admixed and an example in which sintering wasperformed.

EXAMPLE 4

A mixed solution of 50 parts by mass of the octylsilylated fine particletitanium oxide slurry used in Example 1, 5 parts by mass of linseed oil,and 45 parts by mass of decamethylcyclopentasiloxane was filled into acontainer to make a product (surface-treating agent).

One side of a glass plate (5 cm×10 cm×3 mm) having a hydrophilic surfacewas coated with 12 mg of the surface-treating agent and dried at 50° C.for 10 minutes using an air blow dryer. When this glass plate wasrepeatedly placed in and out of running water (4 L/min) at 38° C. forone minute at a rate of 100 times/min slanting at an angle of 30 degreesfrom the horizontal, the fine periodic structure with upward protrusionswas confirmed as shown in FIG. 5.

The width of FIG. 5 is 20 μm.

EXAMPLE 5

20 parts by mass of octylsilylated fine particle zinc oxide slurry usedin Example 1, 20 parts by mass of octylsilylated pigment grade titaniumoxide slurry used in Comparative Example 1, 10 parts by mass of octylpara-methoxycinnamate, 43 parts by mass of decamethylcyclopentasiloxane,5 parts by mass of ethyl alcohol, and 2 parts by mass of atrifluoropropylated trimethylsiloxy silicate solution (a 50% by massdecamethylcyclopentasiloxane solution) were admixed and pulverized andthe resulting solution was filled into a container to make a product(surface-treating agent).

The product of Example 5 exhibited a contact angle of 96 degrees aftercoating and 128 degrees after treatment with water, showing a bigdifference before and after treatment with water.

Next, an aluminum plate was coated with the surface-treating agent ofExample 5 in an amount of 0.2 mg/cm² and sintered at 300° C. for onehour. An example of the scanning electron microscopic photograph of theresulting coating film is shown in FIG. 6.

Further, a glass plate was coated with the surface-treating agent ofExample 5 in an amount of 0.24 mg/cm² and sintered at 300° C. for onehour. An example of the scanning electron microscopic photograph of theresulting coating film is shown in FIG. 7. FIG. 8 is an example of thescanning electron microscopic photograph of the coating film sintered at500° C. for one hour.

In all cases, it is obvious that a fine periodic structure with upwardprotrusions is formed in the coating film.

EXAMPLE 6

100 parts by mass of the surface-treating agent of Example 1 and 2 partsby mass of anatase-type photocatalytic titanium oxide having an averageparticle diameter of 50 nm were admixed and further pulverized using abead mill to prepare a surface-treated film containing titanium oxide,in the same manner as in Example 2. This coating film formed fineroughness. Further, 100 parts by mass of the surface-treating agent ofComparative Example 1 and 2 parts by mass of the abovementionedanatase-type photocatalytic titanium oxide were admixed and furtherpulverized using a bead mill to prepare a surface-treated filmcontaining titanium oxide, in the same manner as in Comparative Example2.

This coating film formed no roughness structure.

Each of the films containing titanium oxide was individually broughtinto contact with an aqueous monochloroacetic acid solution and thenradiated with UV light at a wavelength less than 387 nm. As a result,the initial velocity in disintegrating monochloroacetic acid wasimproved 1.25 times faster for the film with the surface-treating agentof Example 1 than for the film with the surface-treating agent ofComparative Example 1.

INDUSTRIAL APPLICABILITY

As mentioned above, the present invention has industrial applicability,that is, it provides a surface-treating agent characterized in that theaverage primary particle diameter is in the range of 1-50 nm, that itcontains fine particles in the range of 5-60% by mass of the totalamount of the surface-treating agent in a slurry of nanoparticles whichare treated for water repellency and mechanically dispersed in a solventcontaining a volatile solvent, and occasionally a water-repellent resincomponent in the range of 0.1-5% by mass of the total amount of thesurface-treating agent, and that it forms a roughness structure withupward protrusions having a spatial periodicity of 0.1-50 μm on thesurface of a material by volatilizing the solvent or dipping repeatedlyin water upon treating the surface of the material, materials treatedwith this surface-treating agent, and an effective method of thetreatment.

1. A surface-treating agent characterized in that the average primaryparticle diameter is in the range of 1-50 nm, that it contains fineparticles in the range of 5-60% by mass of the total amount of thesurface-treating agent in a slurry of nanoparticles which are treatedfor water repellency and mechanically dispersed in a solvent containinga volatile solvent, and that it forms a roughness structure with upwardprotrusions having a spatial periodicity of 0.1-50 μm on a surface of amaterial by volatilizing the solvent and optionally dipping repeatedlyin water upon treating the surface of the material.
 2. Thesurface-treating agent according to claim 1, wherein the slurry furthercomprises a water-repellent resin component in the range of 0.1-5% bymass of the mass of the surface-treating agent.
 3. The surface-treatingagent according to claim 1, further comprising polymeric resinsincluding monomers and oligomers in addition to the nanoparticle slurrytreated for water repellency.
 4. The surface-treating agent according toclaim 1, characterized in that the treatment for water repellency isselected from alkyl silane treatment, alkyl titanate treatment, andalkyl aluminate treatment.
 5. A material which is obtained by furthersintering a material coated with the surface-treating agent of claim 3and has a roughness structure with upward protrusions having a spatialperiodicity of 0.1-50 μm on the surface.
 6. A highly water-repellentmaterial which is obtained by further treating the material of claim 5for water repellency and has a roughness structure with upwardprotrusions having a spatial periodicity of 0.1-50 μm on the surface. 7.The surface-treating agent according to claim 1, characterized in thatthe admixing amount of a liquid component having a dynamic viscosity ofgreater than 1×10⁻³ m²/s at 25° C. is less than 10% by mass of the massof the surface-treating agent.
 8. The surface-treating agent accordingto claim 1, characterized in that the admixing amount of a liquidcomponent having a dynamic viscosity of greater than 1×10⁻³ m²/s at 25°C. is less than 3% by mass of the mass of surface-treating agent.
 9. Thesurface-treating agent according to claim 1, characterized in that thetreatment for water repellency is octylsilane treatment.
 10. Thesurface-treating agent according to claim 1, characterized in that thenanoparticles are one or more selected from titanium oxide, lowertitanium oxide, zinc oxide, zirconium oxide, aluminum oxide, carbonblack, silicic acid anhydride, cerium oxide, gold, silver, platinum,palladium, rodium, lanthanum, vanadium, tungsten, iron oxide, ironhydroxide and cobalt oxide.
 11. The surface-treating agent according toclaim 1, which forms a roughness surface exhibiting an efficientphotocatalytic effect by admixing a photocatalyst in less than 5% of themass of the surface-treating agent that is a concentration not tointerfere with the roughness formation.
 12. The surface-treating agentaccording to claim 1, characterized in that a wet medium type pulverizeris used as a method of mechanically dispersing nanoparticles treated forwater repellency.
 13. The surface-treating agent according to claim 1,characterized in that it comprises one or more volatile solvents havinga boiling point in the range of 40-99° C. at one atm.
 14. Thesurface-treating agent according to claim 1, characterized in that theboiling point of a volatile solvent used upon preparing a slurry ofnanoparticles treated for water repellency is in the range of 100-260°C. at one atm.
 15. The surface-treating agent according to claim 1,characterized in that the volatile solvent used upon preparing a slurryof nanoparticles treated for water repellency is one or more selectedfrom decamethylcyclopentasiloxane, methyl trimethicone, andtetrakistrimethylsiloxy silane.
 16. The material according to claim 5,characterized in that it is a raw material selected from glass, siliconwafer, fiber, synthetic resins, and optical fiber, or a structurecomprising said raw material.
 17. A method of surface treatmentcharacterized in that a material coated with the surface-treating agentof claim 1 is dried and then further soaked in water, thereby furtherdeveloping roughness on the surface.
 18. A surface-treating agentcomprising: water repellent nanoparticles having an average primaryparticle diameter of 1-50 nm, which accounts for 5-60% by mass of theagent; and a solvent providing a slurry in which the nanoparticles aremechanically dispersed, said solvent containing a volatile solventaccounting for 2-60% by mass of the agent, wherein the surface-treatingagent is configured to self-form a roughness structure with upwardprotrusions having a spatial periodicity of 0.1-50 μm on a surface of amaterial when being applied to the surface and dried.
 19. Thesurface-treating agent according to claim 18, wherein the slurry furthercomprises a water-repellent resin component which accounts for 0.1-5% bymass of the agent.